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                [POI2007]立方体大作战tet                </h1>
                <p>时间限制：10s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：162MB</p>			</div>
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                                <h3>题目描述</h3><p><p>　　一个叫做立方体大作战的游戏风靡整个Byteotia。这个游戏的规则是相当复杂的，所以我们只介绍他的简单规<br />
则：给定玩家一个有2n个元素的栈，元素一个叠一个地放置。这些元素拥有n个不同的编号，每个编号正好有两个<br />
元素。玩家每次可以交换两个相邻的元素。如果在交换之后，两个相邻的元素编号相同，则将他们都从栈中移除，<br />
所有在他们上面的元素都会掉落下来并且可以导致连锁反应。玩家的目标是用最少的步数将方块全部消除。</p></p><hr/><h3>输入格式</h3><p><p>　　第一行包含一个正整数n(1&lt;=n&lt;=50000)。接下来2n行每行一个数ai，从上到下描述整个栈，保证每个数出现且<br />
仅只出现两次(1&lt;=ai&lt;=n)。初始时，没有两个相同元素相邻。并且保证所有数据都能在1000000步以内出解。</p></p><hr/><h3>输出格式</h3><p><p>　　第一行包含一个数m，表示最少的步数。</p></p><hr/><h3>样例输入</h3><pre>样例输入1
5
5
2
3
1
4
1
4
3
5
2
样例输入2
3
1
2
3
1
2
3
</pre><hr/><h3>样例输出</h3><pre>样例输出1
2
样例输出2
3</pre><hr/><h3>提示</h3><p><p><img border="0" alt="" src="../file/1106_0.jpg" /> <img border="0" alt="" src="../file/1106_1.jpg" /></p></p><hr/><h3>题目来源</h3><p>没有写明来源</p>
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